Industrial fermentation processes predominately use glucose as a feedstock for the production of numerous end products, such as proteins, enzymes, amino acids, organic acids, alcohols, biochemicals, pharmaceuticals and the like. In many of these applications glucose is produced from the enzymatic conversion of substrates, which contain starch. Starch accumulates as microscopic granules in plant material and the partial crystalline nature of these granules imparts insolubility in cold water. As a result, many methods have been described for solubilizing starch granules. In particular, many methods have been described for converting starch containing substrates to alcohols, such as ethanol. These methods include direct and indirect heating prior to fermentations (STARCH CHEMISTRY AND TECHNOLOGY, Eds. R. L. Whistler et al., 2nd Ed., (1984) Academic Press Inc,; STARCH CONVERSION TECHNOLOGY Eds., G. M. A. Van Beynum et al., Food Science and Technology Series, Marcel Dekker Inc, NY; and THE ALCOHOL TEXTBOOK 3rd Ed., Eds. K. Jacques et al., (1999), Nottingham University Press). Due to temperature requirements direct and indirect heating methods are energy demanding. Therefore, more recent attention in the industrial fermentation arts and especially in alcohol fermentation has been directed to low energy processes for hydrolyzing granular starch. Low energy processes reduce the need for energy intensive liquefaction cooking steps (U.S. Pat. No. 4,514,496; Ueda et al., (1980) J. Ferment. Tech., 58:237-242; Han et al., (1987) Biotechnol. and Bioeng., 30:225-232; WO 03/066826; WO 03/068976; WO 04/106533; WO 04/081193; WO 05/052148; and US Patent Publication 2005/0266543). A number of novel enzyme compositions capable of hydrolyzing granular (uncooked) starch to produce fermentable glucose in alcohol fermentation processes have been introduced into the market place in the last few years, for example STARGEN (Genencor International Inc.). However, there still remains a need for additional and more effective starch conversion methods, which yield alcohols and high quality fermentation byproducts such as distillers' feeds.
The use of proteases in yeast fermentations has been shown to increase the yield and rate of ethanol production from liquefied starch substrates (U.S. Pat. No. 5,231,017). The NSP24 proteases of the present invention are not only novel proteases but also may be used to increase the ethanol production from insoluble starch substrates.